Hi Pat,
The properties of solder are all VERY temperature dependent--so  "a rule of
thumb you should allow around 40 deg C below the melting point of the solder
being used" does not make any sense. Because the properties change
continuously with temperature, there can be no "threshold limits for solder
temperatures."
Whether or not you have a problem depends entiry on the design details--get
yourself a copy of IPC-D-279.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 386-437-8747, Fax: 386-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com

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